Full-face mask and mask cushion therefor

ABSTRACT

A full-face cushion comprises a substantially triangularly shaped frame from which extends a membrane. The frame has a scalloped edge by which the cushion is affixed to a mask body to form a full-face mask. The membrane has an aperture into which the wearer&#39;s nose is received. The member is spaced away from the rim of the frame, and its outer surface is of substantially the same shape as the rim. Respective notches receive the bridge of the wearer&#39;s nose. The wearer&#39;s nose and lips are received through the aperture into the chamber within the mask body. The seal forming portion thus contacts both the surface of the wearer&#39;s nose and a portion of the wearer&#39;s face in the region between the bottom lip and the chin, and around the sides and over the bridge of the nose. The shape of the seal forming portion is particularly suited to effectively seal the difficult region of the facial contour that is the crease between the sides of the nose and the face.

This is a CIP of Ser. No. 08/791,212 filed Jan. 31, 1997.

FIELD OF THE INVENTION

The invention relates generally to a full-face (ie. nose and mouth) mask and to a cushion therefor, for example, for use in the treatment of respiratory conditions and in assisted respiration.

BACKGROUND OF THE INVENTION

Full-face masks are commonly used in the treatment of respiratory conditions and sleep disorders (e.g., obstructive sleep apnea) by delivering a flow of breathable gas for, or to assist, patient respiration. These masks typically receive a gas supply line which delivers gas into a chamber formed by walls of the mask The walls usually are semi-rigid and have a face contacting portion including an aperture which is generally aligned with the wearer's nostrils and mouth. The face contacting portion can comprise a soft, resilient elastomeric material which may conform to various facial contours. The mask normally is secured to the wearer's head by straps. The straps are adjusted to pull the mask against the face with sufficient force to achieve a gas tight seal between the mask and the wearer's face. Gas is thus delivered to the mask and through the aperture to the wearer's nasal passages and throat.

Problems often arise with masks of the above configuration. For example, the mask may be dislodged, thereby breaking the seal between the mask and wearer. This may occur if the wearer rolls over when sleeping thereby creating a drag force on the gas supply line which is transmitted to the mask, breaking the seal. In the case of a mask being used for the administration of Continuous Positive Airway Pressure (CPAP) treatment for the condition obstructive sleep apnea, such a leak can result in the pressure supplied to the entrance of the wearer's airway being below the therapeutic value, and the treatment becoming ineffective.

Another problem is that the face contacting portion may apply excessive pressure to the wearer's face resulting in discomfort and possibly skin irritation. This can occur because the face contacting portion has to distort beyond its normal range of elasticity to conform to certain facial contours which requires the application of excessive forces. In some cases these excessive pressures and forces may cause the face to distort to conform with the face contacting portion to increase wearer discomfort, facial soreness and ulceration.

It is an object of the invention to overcome or at least substantially ameliorate one or more of the foregoing disadvantages.

SUMMARY OF THE INVENTION

In one broad form, the invention discloses a full-face mask cushion to sealingly connect a mask to a wearer's face, the cushion comprising:

-   -   a nasal bridge region, a cheek region and a chin region;     -   a first membrane comprising a substantially triangularly-shaped         frame of resilient material having a first molded inwardly         curved rim;     -   a second membrane of resilient material, said second membrane         being thinner than said first membrane, said second membrane         having a second molded inwardly curved rim, said second membrane         curved rim spaced a first distance from said first membrane         curved rim in said cheek region and said second membrane curved         rim spaced a second distance from said first membrane curved rim         in said nasal bridge region, said second distance greater than         said first distance, said distances measured when the mask is         not in use, a portion of said second membrane curved rim forming         a face contacting seal.

Preferably, the rim and seal portion are shaped to generally match facial contours of the facial tissue around the sides and over the bridge of the nose and between the bottom lip and the chin.

In one particularly advantageous form, the membrane is substantially saddle-shaped. The membrane further has a centrally located aperture through which the wearer's nose and mouth pass to enter said cavity.

It is preferred that the cushion and membrane each include a co-located notch to accommodate the bridge of the nose of the wearer. Typically, the seal portion contacts at least the wearer's nose, and preferably, also the facial tissue around the sides and over the bridge of the nose and between the bottom lip and the chin.

The invention further discloses a full-face mask for connection to a wearer's face comprising:

-   -   a mask body for connection with a supply of breathable gas; and     -   a full-face cushion secured to said mask body, the body and         cushion forming a nose and mouth-receiving cavity, said cushion         including:     -   a nasal bridge region, a cheek region and a chin region;     -   a substantially triangularly-shaped first membrane of resilient         material having a first molded inwardly curved rim to surround         wearer's nose;     -   a second membrane also of resilient material, said second         membrane being relatively more flexible than said first         membrane, said second membrane having a second molded inwardly         curved rim, said second molded rim being of the same general         shape as said first molded rim and fixed to and extending away         from said first membrane so as to have a second membrane inner         surface spaced a first distance from an outer surface of said         first molded rim in said cheek region and said second membrane         inner surface spaced a second distance from said first membrane         outer surface of said first molded rim in said nasal bridge         region, said second distance greater than said first distance,         said distances measured when the mask is not in use, a portion         of said second molded rim forming a face contacting seal; and     -   wherein said seal portion is substantially coterminous with         respect to said second molded rim and is resiliently deformable         towards said first membrane in use of said mask.

The mask body can further include attachment points from which securing straps can be attached, and by which the mask can be secured to the wearer's head. The nasal mask can yet further comprise an arm depending from said body from which a further securing strap(s) can be attached.

The invention further discloses a CPAP treatment apparatus comprising:

-   -   a flow generator for the supply of gas at a pressure elevated         above atmospheric pressure;     -   a gas delivery conduit coupled to said flow generator; and     -   a full-face mask in turn coupled to said conduit to said nasal         mask including:     -   a mask body for connection with a supply of breathable gas; and     -   a full-face cushion secured to said mask body, the body and         cushion forming a nose and mouth-receiving cavity, the cushion         including:     -   a nasal bridge region, a cheek region and a chin region;     -   a substantially triangularly-shaped first membrane of resilient         material having a first membrane having a molded inwardly curved         rim;     -   a second membrane having a second molded inwardly curved rim         also of resilient material, said second membrane being         relatively more flexible than said first membrane, and being of         the same general shape as said first molded inwardly curved rim         and fixed to and extending away from said first membrane so as         to have an inner surface spaced a first distance from said first         molded rim in said cheek region and said second membrane inner         surface spaced a second distance from said first molded rim,         said second distance greater than said first distance, said         distances measured when the mask is not in use, a portion of         said second molded rim forming a face contacting seal; and     -   wherein said seal portion is generally coterminous with respect         to said second molded rim and is resiliently deformable towards         said first membrane in use of said mask.

In one particularly preferred form, a supply of gas can be provided to said cavity, said supply of gas assisting, but not solely causing maintenance of a seal by said seal forming portion of said membrane to the face of the wearer in use of the cushion.

Advantageously, because the membrane and the rim are substantially shaped to the facial contour, and the membrane does not need to turn in on itself, as in the prior art, thus contacting the face without folds or creases. With the cushion/mask secured to the wearer's head, the headstraps need only to be tensioned to balance the force due to mask gas pressure that tends to lift the mask off the face. Such relatively lower mask-to-face pressure results in greater patient comfort, and a reduction in the likelihood of skin irritation.

BRIEF DESCRIPTION OF THE DRAWINGS

An embodiment of the invention will now be described with reference to the accompanying drawings, in which:

FIG. 1 is a rear perspective view of a nasal mask cushion embodying the present invention;

FIG. 2 is a cross-sectional view of the cushion shown in FIG. 1 along line 2-2;

FIG. 3 is a perspective view of a nasal mask including the cushion of FIG. 1;

FIG. 4 is a perspective view of the nasal mask of FIG. 3 secured to a wearer's head;

FIG. 5 is a side view of the mask cushion shown in FIG. 1;

FIG. 6 is a front view of the mask cushion shown in FIG. 1;

FIG. 7 is a rear view of the mask cushion shown in FIG. 1;

FIG. 8 is a cross sectional view of the mask shown in FIG. 1 along line 8-8 of FIG. 7;

FIG. 9 is a cross sectional view of the mask shown in FIG. 1 along line 9-9 of FIG. 7;

FIG. 10 is a front perspective view of a full-face mask cushion embodying the present invention;

FIG. 11 is a perspective view of a full-face mask including the cushion of FIG. 10;

FIG. 12 is an underside view of the mask cushion shown in FIG. 10;

FIG. 13 is a front view of the mask cushion shown in FIG. 10;

FIG. 14 is a rear view of the mask cushion shown in FIG. 10;

FIG. 15 is a cross sectional view of the mask cushion shown in FIG. 10 along line 15-15 of FIG. 14;

FIG. 16 is a cross sectional view of the mask cushion shown in FIG. 10 along line 16-16 of FIG. 14; and

FIG. 17 is a perspective view of the mask shown in FIG. 11 secured to a wearer's face.

DESCRIPTION OF THE PREFERRED EMBODIMENTS

FIGS. 1 to 9 show a nasal cushion 30A and a nasal mask 60A embodying the present invention.

FIG. 1 is a perspective view of the nasal cushion 30A. FIG. 3 is a perspective view of the nasal cushion 30A attached to a mask body 46 to form the nasal mask 60A.

The nasal cushion 30A comprises a substantially triazgularly shaped frame 32 from which extends a membrane 34. The frame 32 has a scalloped edge 36 by which the nasal cushion 30A is affixed to the mask body 46, as presently will be described.

The membrane 34 has an aperture 38 into which the wearer's nose is received in use of the nasal cushion 30A. The membrane 34 is spaced away from the rim 40 of the frame 32, and its outer surface 41 is of substantially the same shape as the rim 40. The outer surface 41 of the membrane 34 and the rim 40 of the frame 32 also can be described as generally saddle shaped. The shaping of the outer surface 41 of the membrane 34 and the rim 40 of the frame 32 also include respective notches 42,44 that receive the bridge of the wearer's nose in use of the nasal cushion 30A.

As is best seen in FIG. 2, the frame 32 and the membrane 34 are integrally formed, typically in a one-shot molding process. The frame 32 and the membrane 34 are fabricated from a resilient material. One suitable such material is SILASTIC™ silicone elastomer manufactured by Dow Corning. The frame 32, in a preferred embodiment, has a typical thickness at its rim 40 of 1.5 mm The membrane 34, in a preferred embodiment, has a typical thickness of 0.35 mm. In this way, the membrane 34 is relatively more flexible than the rim 40.

In use of the nasal cushion 30A, a wearer's nose will be inserted in the aperture 38 to engage a seal forming portion 45 (formed between the dashed lines) of the outer surface 41 to cause deformation of the membrane 34. Depending upon the securing force supplied to the membrane 34, it may deform to a point where it butts against the rim 40 of the frame 32. The frame 32 has a rigidity sufficient to withstand usual securing pressures in use of the nasal cushion 30A to tend to retain its shape and resist deformation. It thus acts as a supporting structure.

Referring now to FIG. 3, the nasal cushion 30A is shown attached to the mask body 46 by the edge 36 of the frame 32, adhered or otherwise secured to a flange 48 of the mask body 46. Only the outer surface 41 of the membrane 34 can be seen. The flange 48 includes two lower slots 50 and 54 from which a first tensioning strap 68 can be attached to secure the cushion 30 and the mask body 46 (in combination) to the head of a wearer.

The mask body 46 forms a cavity that can receive the nose of the wearer by the aperture 38. A port 56 is provided at the top of the mask body 46 by which breathable gas can be supplied to the chamber.

Referring now to FIG. 4, a coupling tube 62 is shown above the nasal mask 60A. The coupling tube 62 is connected at one end with the inlet port 56, and at the other to a socket 64 into which can be received a gas delivery tube 65 for the supply of breathable gas to the chamber internal of the mask body 46 from a flow generator 67. The mask body 46 also has two vent openings 66 by which expired gas is exhausted. The first fastening strap 68 is fixed between the two lower slots 50,54. An upper slot 52 receives an arm 70, the top end of which has a resilient pad 72 to engage the forehead of the wearer. The arm 70 has two slots, only one slot 74 shown, along its side edges, by which a second fastening strap 78 is secured.

In fitting the nasal mask 60A, the wearer's nose is received through the aperture 38 into the chamber within the mask body 46. The seal forming portion 45 thus contacts both the surface of the wearer's nose and a portion of the wearer's face in the region between the base of the nose and the upper lip, and around the sides and over the bridge of the nose. The shape of the seal forming portion 45 is particularly suited to effectively seal the difficult region of the facial contour that is the crease between the sides of the nose and the face. Depending upon the tension applied by the first and second fastening straps 68,78, a seal is formed with the membrane 34 remaining spaced from the rim 40 of the cushion frame 32. While the provision of pressurised gas to the chamber of the mask body 46 assists in the maintenance of a seal between the membrane 34 and the wearer's nose and face, it is not essential in most cases, and an effective seal will be formed absent any such pressurised gas. When relative movement of the nasal mask 60A in relation to the wearer's head, the nose will be restrained by contacting the frame 32. Thus only limited relative motion between the nasal mask 60A and the wearer's nose and face occurs.

The membrane 34 closely imitates the facial contour, and because of its relatively lesser stiffness than the frame 32, can conform to particular facial structures with minimum force, and without a tendency to fold or crease.

If the fastening straps 68 and 78 are tensioned to excess, the membrane 34 deforms to abut the rim 40 of the cushion 30A, the frame 32 thus acting as an “end limit”. In such a configuration, almost zero relative movement can occur between the nasal mask 60A and the wearer's head.

FIGS. 10 to 17 show a full-face cushion 30B and a full-face mask 60B embodying the present invention. Like reference numerals to those used in describing the “nasal” embodiment of FIGS. 1 to 9 shall be used to denote like features of the “full-face” embodiment of FIGS. 10 to 17.

FIG. 10 is a perspective view of the full-face cushion 30B. FIG. 11 is a perspective view of the full-face cushion 30B attached to a mask body 46 to form the full-face mask 60B.

The full-face cushion 30B comprises a substantially triangularly shaped frame 32 from which extends a membrane 34. The frame 32 has a scalloped edge 36 by which the full-face cushion 30B is affixed to the mask body 46, as presently will be described.

The membrane 34 has an aperture 38 into which the wearer's nose and lips are received in use of the full-face cushion 30B. The membrane 34 is spaced away from the rim 40 of the frame 32, and its outer surface 41 is of substantially the same shape as the rim 40. The outer surface 41 of the membrane 34 and the rim 40 of the frame 32 also can be described as generally saddle shaped. The shaping of the outer surface 41 of the membrane 34 and the rim 40 of the frame 32 also include respective notches 42,44 that receive the bridge of the wearer's nose in use of the full-face cushion 30B.

As is best seen in FIG. 16, the frame 32 and the membrane 34 are integrally formed, typically by in a one-shot molding process. The frame 32 and the membrane 34 are fabricated from a resilient material. One suitable such material is SILASTIC silicone elastomer manufactured by Dow Corning. The frame 32, in a preferred embodiment, has a typical thickness at its rim 40 of 1.5 mm. The membrane 34, in a preferred embodiment, has a typical thickness of 0.35 mm. In this way, the membrane 34 is relatively more flexible than the rim 40.

In use of the full-face cushion 30B, a wearer's nose and lips will be inserted in the aperture 38 to engage a seal forming portion 45 (formed inside the dashed line, see FIG. 13) of the outer surface 41 to cause deformation of the membrane 34. Depending upon the securing force supplied to the membrane 34, it may deform to a point where it butts against the rim 40 of the frame 32. The frame 32 has a rigidity sufficient to withstand usual securing pressures in use of the full-face cushion 30B to tend to retain its shape and resist deformation. It thus acts as a supporting structure.

Referring now to FIG. 11, the full-face cushion 30B is shown attached to the mask body 46 by the edge 36 of the frame 32, adhered or otherwise secured to a flange 48 of the mask body 46. Only the outer surface 41 of the membrane 34 can be seen. The mask body 46 includes two lower slots 50 and 54 and two upper slots 74 and 76 from which first and second tensioning straps 68 and 78 can respectively be attached to secure the cushion 30B and the mask body 46 (in combination) to the head of a wearer.

The mask body 46 forms a cavity that can receive the nose and lips of the wearer by the aperture 38. A port 56 is provided at the front of the mask body 46 by which breathable gas can be supplied to the chamber.

Referring now to FIG. 17, a coupling elbow 62 is shown connected at one end with the inlet port 56, and at the other to a socket 64 into which can be received a gas delivery tube 65 for the supply of breathable gas to the chamber internal of the mask body 46 from a flow generator 67. The mask body 46 also a vent opening 66 by which expired gas is exhausted. The first fastening strap 68 is fixed between to the lower two slots 50 and 54. The second fastening strap 78 is secured between the two upper slots 74 and 76. The first and second straps 68 and 78 are joined at each side by a bridging portion 79.

In fitting the full-face mask 60B, the wearer's nose and lips are received through the aperture 38 into the chamber within the mask body 46. The seal forming portion 45 thus contacts both the surface of the wearer's nose and a portion of the wearer's face in the region between the bottom lip and the chin, and around the sides and over the bridge of the nose. The shape of the seal forming portion 45 is particularly suited to effectively seal the difficult region of the facial contour that is the crease between the sides of the nose and the face. Depending upon the tension applied by the first and second fastening straps 68,78, a seal is formed with the membrane 34 remaining spaced from the rim 40 of the cushion frame 32. While the provision of pressurised gas to the chamber of the mask body 46 assists in the maintenance of a seal between the membrane 34 and the wearer's nose and face, it is not essential in most cases, and an effective seal will be formed absent any such pressurised gas. When relative movement of the full-face mask 60B in relation to the wearer's head, the nose will be restrained by contacting the frame 32. Thus only limited relative motion between the full-face mask 60B and the wearer's nose and face occurs.

The membrane 34 closely imitates the facial contour, and because of its relatively lesser stiffness than the frame 32, can conform to particular facial structures with minimum force, and without a tendency to fold or crease.

If the fastening straps 68 and 78 are tensioned to excess, the membrane 34 deforms to abut the rim 40 of the cushion 32, the frame 32 thus acting as an “end limit”. In such a configuration, almost zero relative movement can occur between the full-face mask 60B and the wearer's head.

The nasal cushion 30A, the nasal mask 60A, the full-face cushion 30B and the full-face mask 60B have been described with reference to CPAP or assisted respiration treatment, however it is to be understood that the invention generally is applicable to any application where gas and/or atomised liquid is to be supplied to the entrance of the airways. Such applications include nebulisers, gas masks and anaesthetic machines. 

1-25. (canceled)
 26. A mask assembly for delivery of a supply of gas to an entrance to the airways of a patient, said patient having a nasal bridge region, a cheek region and a chin region, said mask assembly comprising: a headstrap system to secure the mask assembly relative to the patient's head; and a cushion adapted to confront a face of a patient, said cushion comprising first and second membranes of integrally formed elastomeric material, said first and second membranes having respective first and second distal ends delimiting respective first and second apertures adapted to receive the patient's nose and mouth, said first distal end terminating adjacent the second aperture, said second membrane defines a seal-forming portion on an outer surface thereof, said seal-forming portion being constructed and arranged to be positioned adjacent a nasal bridge region, along sides of the nose, and below lips or on a chin to effect a seal, the seal forming portion is structured such that it is not required to turn in on itself to conform with the patient's face, said first membrane provides a supporting structure for the second membrane, and said second membrane covering said first membrane.
 27. The mask assembly of claim 26, wherein the second membrane is substantially unsupported by the first membrane where the cushion is adapted to seal with the nasal bridge region.
 28. The mask assembly of claim 26, wherein, in a portion of the cushion adapted to contact the chin region, the first and second membranes extend a chin region distance towards the aperture, the chin region distances of the rims being generally equal.
 29. The mask assembly of claim 26, wherein, in a portion of the cushion adapted to contact the cheek region, the second membrane extends a cheek region distance towards the aperture that is greater than the chin region distance of the second membrane.
 30. The mask assembly of claim 28, wherein, in the nasal bridge region, the second membrane extends a nasal bridge region distance that is greater than the chin region distance of the second membrane.
 31. The mask assembly of claim 30, wherein in the nasal bridge region, the second membrane extends towards the aperture to a degree relative to the first membrane that is greater than that of the second membrane relative to the first membrane in the cheek region.
 32. The mask assembly of claim 26, wherein, in the nasal bridge region, the shape between the first and second membranes is different from one another such that the nasal bridge is able to be inserted into a space where there is substantially no first membrane, with the second membrane stretching across a gap in the first membrane.
 33. The mask assembly of claim 26, further comprising a notch in both the first and second membranes to receive the bridge of the wearer's nose.
 34. The mask assembly of claim 26, wherein the first membrane has a thickness of about 1.5 mm and the second membrane has a thickness of about 0.35 mm.
 35. The mask assembly of claim 26, wherein the first membrane extends a first distance towards the aperture in the nasal bridge region, and a second distance towards the aperture in the chin region, wherein said first distance is less than said second distance.
 36. A mask assembly for delivery of a supply of gas to an entrance to the airways of a patient, said patient having a nasal bridge region, a cheek region and a chin region, said mask assembly comprising: a headstrap system to secure the mask assembly relative to the patient's head; and a cushion adapted to confront a face of a patient, said cushion comprising: first and second membranes of integrally formed elastomeric material, each of said first and second membranes having a proximal portion and a distal end, the distal ends defining respective first and second apertures adapted to receive the patient's nose and mouth, proximal portions intersecting one another, and the first and second membranes extending in spaced relation to one another toward the respective distal ends; and a support portion from which the first and second membranes extend, the support portion including an edge configured to connect the cushion to a mask body, said second membrane defines a seal-forming portion on an outer surface thereof, said seal-forming portion being constructed and arranged to be positioned adjacent a nasal bridge region, along sides of the nose, and below lips or on a chin to effect a seal, the seal forming portion is structured such that it is not required to turn in on itself to conform with the patient's face, said first membrane provides a supporting structure for the second membrane, and said second membrane covering said first membrane.
 37. The mask assembly of claim 36, wherein the second membrane is substantially unsupported by the first membrane wherein the cushion is adapted to seal with the nasal bridge region.
 38. The mask assembly of claim 36, wherein, a portion of the cushion adapted to contact in the chin region, the first and second membranes extend a chin region distance towards the aperture, the chin region distance of the second membrane being greater than the chin region distance of the first membrane.
 39. The mask assembly of claim 38, wherein, in a portion of the cushion adapted to contact the cheek region, the second membrane extends a cheek region distance towards the aperture that is greater than the chin region distance of the second membrane.
 40. The mask assembly of claim 38, wherein, in the nasal bridge region, the second membrane extends a nasal bridge region distance that is greater than the chin or cheek region distances of the second membrane.
 41. The mask assembly of claim 40, wherein in the nasal bridge region, the second membrane extends towards the aperture to a degree relative to the first membrane that is greater than that of the second membrane relative to the first membrane in the cheek and chin regions.
 42. The mask assembly of claim 36, wherein, in the nasal bridge region, the shape between the first and second membranes is different from one another such that the nasal bridge is able to be inserted into a space where there is substantially no first membrane, with the second membrane stretching across a gap in the first membrane.
 43. The mask assembly of claim 36, further comprising a notch in both the first and second membranes to receive the bridge of the wearer's nose.
 44. The mask assembly of claim 36, wherein the first membrane has a thickness of about 1.5 mm and the second membrane has a thickness of about 0.35 mm.
 45. A mask assembly for delivery of a supply of gas to an entrance to the airways of a patient, said patient having a nasal bridge region, a cheek region and a chin region, said mask assembly comprising: a headstrap system to secure the mask assembly relative to the patient's head; and a cushion adapted to confront a face of a patient, said cushion comprising: first and second membranes of integrally formed elastomeric material, each of said first and second membranes having an aperture adapted to receive the patient's nose and mouth, each of the first and second membranes having a distal end and a proximal end, the proximal ends intersecting one another and the first and second membranes extending in spaced relation to one another toward the respective distal ends, said second membrane defines a seal-forming portion on an outer surface thereof, said seal-forming portion being constructed and arranged to be positioned adjacent a nasal bridge region, along sides of the nose, and below lips or on a chin to effect a seal, said first membrane provides a supporting structure for the second membrane, and said second membrane covering said first membrane, wherein the second membrane has a variable dimension suited to the nasal bridge region, the cheek region and the chin region, wherein the first membrane has a variable dimension suited to the nasal bridge region, the cheek region and the chin region, and/or the first and second membranes have variable widths relative to one another suited to the nasal bridge region, the cheek region and the chin region.
 46. The mask assembly of claim 45, wherein the second membrane is substantially unsupported by the first membrane where the cushion is adapted to seal with the nasal bridge region.
 47. A mask assembly for delivery of a supply of gas to an entrance to the airways of a patient, said patient having a nasal bridge region, a cheek region and a chin region, said mask assembly comprising: a headstrap system to secure the mask assembly relative to the patient's head; and a cushion adapted to confront a face of a patient, said cushion comprising: first and second membranes of integrally formed elastomeric material, each of said first and second membranes having an end forming a respective rim defining an aperture through which the patient's nose and mouth, said second membrane defines a seal-forming portion on an outer surface thereof, said seal-forming portion being constructed and arranged to be positioned adjacent a nasal bridge region, along sides of the nose, and below lips or on a chin to effect a seal, the seal forming portion is structured such that it is not required to turn in on itself to conform with the patient's face, said first membrane provides a supporting structure for the second membrane, said second membrane covering said first membrane, and wherein the second membrane is substantially unsupported by the first membrane where the cushion is adapted to seal with the nasal bridge region in use.
 48. The mask assembly of claim 47, wherein, a portion of the cushion adapted to contact in the chin region, the first and second membranes extend a chin region distance towards the aperture, the chin region distance of the second membrane being greater than the chin region distance of the first membrane.
 49. The mask assembly of claim 48, wherein, in a portion of the cushion adapted to contact the cheek region, the second membrane extends a cheek region distance towards the aperture that is greater than the chin region distance of the second membrane.
 50. The mask assembly of claim 48, wherein, in the nasal bridge region, the second membrane extends a nasal bridge region distance that is greater than the chin or cheek region distances of the second membrane.
 51. The mask assembly of claim 50, wherein in the nasal bridge region, the second membrane extends towards the aperture to a degree relative to the first membrane that is greater than that of the second membrane relative to the first membrane in the cheek and chin regions.
 52. The mask assembly of claim 47, wherein, in the nasal bridge region, the shape between the first and second membranes is different from one another such that the nasal bridge is able to be inserted into a space where there is substantially no first membrane, with the second membrane stretching across a gap in the first membrane.
 53. The mask assembly of claim 47, further comprising a notch in both the first and second membranes to receive the bridge of the wearer's nose.
 54. The mask assembly of claim 47, wherein the first membrane has a thickness at its rim of about 1.5 mm and the second membrane has a thickness at its rim of about 0.35 mm.
 55. A mask assembly for delivery of a supply of gas to an entrance to the airways of a patient, said patient having a nasal bridge region, a cheek region and a chin region, said mask assembly comprising: a headstrap system to secure the mask assembly relative to the patient's head; and a cushion adapted to confront a face of a patient, said cushion comprising: first and second membranes of integrally formed elastomeric material, each of said first and second membranes having an aperture through which the patient's nose and mouth are received, said second membrane defines a seal-forming portion on an outer surface thereof, said seal-forming portion being constructed and arranged to be positioned adjacent a nasal bridge region, along sides of the nose, and below lips or on a chin to effect a seal, said first membrane provides a supporting structure for the second membrane, and said second membrane covering said first membrane, wherein the second membrane has a variable dimension suited to the nasal bridge region, the cheek region and the chin region, the first membrane has a variable dimension suited to the nasal bridge region, the cheek region and the chin region, and/or the first and second membranes have variable widths relative to one another suited to the nasal bridge region, the cheek region and the chin region, and wherein the second membrane is substantially unsupported by the first membrane where the cushion is adapted to seal with the nasal bridge region in use.
 56. The mask assembly of claim 26, wherein first and second membranes extend in spaced relation to one another.
 57. The mask assembly of claim 26, wherein the cushion comprises a support portion from which the first and second membranes extend, the support portion including an edge configured to connect the cushion to a mask body. 